The present invention relates to a signal recording/reproducing apparatus for high-density recording/reproducing of data.
Recently, improvement for digital magnetic recording/reproducing apparatus such as floppy disk apparatus is being made for recording-capacity increasing purposes. This is also being made for magnetic tape apparatus and hard disk apparatus. For increasing the recording capacity in the magnetic recording/reproducing apparatus, required is heightening the area recording density of the recording medium, which in turn depends upon improvement of the linear density in the track longitudinal directions and improvement of the latitudinal-direction density due to narrowing the track pitch. For example, in order to meet the requirement of heightening the linear recording density, an equalizer is used for suppressing the interference between codes in a reproduced signal, and on the other hand, for improving the track density, high-accuracy tracking servo techniques for recording/reproducing heads have been developed. The conventional track-density improving techniques are exemplified by description in reports such as "High-Density Floppy Desk, Realizing High Track Density by Tracking Servo Technique Based upon Modern Control Theory" (Nikkei Electronics, No. 431, P181-194, Oct. 5, 1988) and "Matsushita Electric Industrial Co., Ltd has also Manufactured 16-Mbyte Capacity and 50-msec average access time 3.5 Inch Floppy Disk Drive" (Nikkei Electronics, No. 460, P98-99, Nov. 14, 1988), where for narrowing the track pitch the recording/reproducing head is tracking-controlled by means of a mechanical drive system. One example of the conventional techniques will be described hereinbelow with reference to FIGS. 1 to 3. In FIG. 1 showing an arrangement of the conventional signal recording/reproducing apparatus, illustrated at numeral 1 is a recording medium which is rotatable at a constant speed of 360 revolutions per minute by means of a recording medium drive device 2. As shown in FIG. 2, recording data are recorded on the recording medium 1 so as to form concentrically circled recording tracks each comprising sectors. The recording/reproducing of the data is effected in units of sector. As illustrated in FIG. 3, in each sector is pre-recorded sector servo information which is padding servo data for detection of a tracking signal for a recording/reproducing head. Data writing is not performed for the region of the sector servo information and the sector servo information is reproduced in synchronism with the rotation of the recording medium 1 even during recording. In FIG. 3, character WT represents a track width and character PT designates a track pitch.
Returning again to FIG. 1, a recording/reproducing head 3 is arranged to be brought into contact with the recording medium 1 and to be positioned by a head drive section 4 so as to be relatively movable with respect to the recording medium 1 in longitudinal directions of tracks forming concentric circles as illustrated in FIG. 2. The recording/reproducing head 3 is arranged to be selectively coupled through a switch 5 to a recording amplifier 6 and a reproducing amplifier 7, that is, the switch 5 performs switching operation so that the recording/reproducing head 3 is coupled to the recording amplifier 6 during recording and on the other hand switchable to be coupled to the reproducing amplifier 7 during reproducing as illustrated in FIG. 1. The reproducing amplifier 7 is coupled to a head control circuit 8 which is responsive to the output thereof so as to detect the sector servo information to check the difference in position between the recording/reproducing head 3 and the recording track of the recording medium 1. The output of the head control circuit 8 which represents the position difference therebetween is supplied to the above-mentioned head drive section 4. The head control circuit 8, together with the head drive section 4, makes up a head control section which performs control so that the output level of the head control circuit 8 becomes small, that is, the recording/reproducing head 3 follows the recording track.
During recording, the parallel data of the recording data for which error correction code control (which will hereinafter be referred to as ECC) process are effected are inputted to a recording-data processer 9. The recording-data processor 9 performs modulation such as run length limited code (2, 7), which will hereinafter be referred to as RLLC(2,7), with respect to the inputted parallel data and then outputs serial data to the recording amplifier 6. The recording amplifier 6 current-drives the recording/reproducing head 3 in accordance with the recording data for recording. On the other hand, for reproducing, the reproducing amplifier 7 amplifies and outputs a reproduction signal due to the recording/reproducing head 3, the outputted reproduction signal being supplied to a data detection section 10 so as to detect the data signal. The detected data signal is fed to a format controller 11 which performs demodulation such as RLLC(2, 7) with respect thereto to obtain the original recording data which are in turn ECC-processed, for example.
Here, although a tracking error of about 20 microns generally occurs because of eccentricity in mounting the recording medium on the apparatus and the difference in position between the recording track and the reproducing track due to deformation of the recording medium, the tracking error can be reduced up to below 2 microns by means of the above-described processes. In this case, the minimum track pitch which can be realized is about 45 microns whereby the track density can reach 400 to 500 tracks per inch. When the linear recording density in the track longitudinal direction is 35 Kbits per inch and recording is performed for both surfaces of a floppy disk whose diameter is 3.5 inches, the recording capacity results in being about 10 Mbytes. Generally, the prior art utilizes mechanical means in order to narrow the track pitch. That is, the mechanical accuracy is arranged to be increased or a mechanical control such as tracking control is executed, thereby resulting in increase of the track density.
For further enhancing the recording capacity, there is a problem which arises with such a conventional signal recording/reproducing apparatus, however, in that the recording format used therein provides difficulty to realize the follow error below 2 microns to make it difficult to allow a narrow track pitch below 10 microns. For example, the size of the recording/reproducing head may be decreased in accordance with the thin-film technology so that the recording track width reaches below 10 microns. Illustratively, a multi-track thin-film head may be used to decrease the track pitch up to about 10 microns. Although the track pitch narrowing depends upon the fabrication accuracy of the thin film, there is a possibility that the track pitch may be further decreased in the future. However, an important problem for narrowing the track pitch in the conventional techniques relates to improvement of the mechanical accuracy including the tracking control accuracy, rather than the size-reduction. In addition, another problem relates to difficulty to meet the recent requirement for increasing the transfer rate in units of time. In the conventional technique, although for improving the transfer rate it is required to heighten the relative speed of the recording medium to the recording/reproducing head, difficulty is encountered to increase the relative speed thereof concurrently with performing the tracking control of the recording/reproducing head, particularly, in the apparatus such as floppy disk system in which the recording/reproducing head is arranged to be brought into contact with the recording medium.